If you wanna be some great guitarist you need to devote all of your time. If you wanna be like me, just practice 4 hrs everyday. If you wanna be like my brother, you dont have to practice at all (cos' he dont know how to play). So it all depend upon your goal.
If you are not serious about it and just wanna play few songs infront of some chicks than it wont take you more than couple of months. Best of Luck...